Many applications in the physical and life sciences require exciting a sample with a certain wavelength or precise wavelength sweeps over time. A tunable laser is often used to provide the excitation radiation with the wavelength being changed accordingly.
In order to change the wavelength in a laser cavity the cavity needs to be comprised of a broadband gain element and a wavelength selective element or a combination of several elements which together act as a wavelength filter. Examples of a wavelength filter are a birefringent tuning plate or a combination of two prisms, an aperture, and a retro reflector. In the latter case, the light inside the laser cavity is separated by wavelength through the prisms and the aperture filters out the desired wavelength. In order to change the wavelength the aperture or the second prism can be moved. Particularly in modelocked lasers the latter case can be advantageous as it allows manipulating the net cavity dispersion while changing the wavelength. The movement of the prism needs to be smooth and precise as it is part of the cavity. In existing solutions the prism is often moved using a combination of an encoded servo or stepper motor and a lead screw driven translation stage. This setup suffers from slow tuning speed and is subject to wear over time. Many experiments particularly in the life science community try to study the temporal evolution of certain samples and require rapid wavelength jumps or sweeps. Existing solutions have failed so far to satisfy these needs.
The present invention provides a solution to the technical problem of how to change the wavelength of a laser an order of magnitude faster than existing solutions without sacrificing the accuracy of the scan. This invention enables doing experiments which used to require two, synchronized lasers to be done with just one laser.